1. Field of the Invention
The present invention relates to a semiconductor process. More particularly, the present invention relates to a photoresist trimming process that is conducted to reduce the linewidth of photoresist patterns formed on semiconductor wafers.
2. Description of the Related Art
In advanced semiconductor processes, a narrower linewidth of a patterned wafer layer can be made by trimming the photoresist patterns for defining the wafer layer prior to the corresponding etching step of the wafer layer. A photoresist trimming process can be conducted in a transformer coupled plasma (TCP) etcher, which usually includes an electrostatic chuck for holding a wafer, a thermometer on the electrostatic chuck for measuring the temperature in the etching chamber, and a TCP window of dielectric material in the etching chamber that allows RF power to be transmitted to the plasma generation zone of the etching chamber.
However, in a conventional photoresist trimming process, many season wafers, approximately in a number up to 25, must be treated sequentially through the etching chamber before the target wafers are treated, so that the degree of photoresist trimming on the target wafers can be kept stable to ensure uniformity of critical dimension (CD). Accordingly, many wafers are wasted as season wafers in a conventional photoresist trimming process, so that the manufacturing cost of the product is increased.